aws-lambda-event-sources: SQS receiveMessageWaitTime's default value is incorrect

[sarisia]

Describe the issue

Docs for aws-lambda-event-sources says SQS Queue's receiveMessageWaitTime property is default to 20 seconds,
but according to CDK aws-sqs docs and CloudFormation AWS::SQS::Queue docs, it's 0 seconds by default, not 20 seconds.

Links

• CDK aws-lambda-event-sources
  https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda_event_sources-readme.html#sqs

  receiveMessageWaitTime: Will determine long poll duration. The default value is 20 seconds.

• CDK aws-sqs
  https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_sqs.Queue.html#receivemessagewaittime

  receiveMessageWaitTime?
  Type: Duration (optional, default: 0)

• CloudFormation AWS::SQS::Queue
  https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-sqs-queue.html#aws-resource-sqs-queue-properties

  ReceiveMessageWaitTimeSeconds
  ... You can specify an integer from 1 to 20. Short polling is used as the default or when you specify 0 for this property. ...

[pahud]

Yes this is confusing. But it's unclear to me what the default duration is from the CFN document while according to this document, the default value seems to be 0. Are you interested to create a PR for this?

[sarisia]

Are you interested to create a PR for this?

Yeah I'm happy to take care of it!

BTW, I suspect that SQS's receiveMessageWaitTime won't affect the Lambda's internal SQS poller's behaviour. I saw some users pointed out that Lambda's poller ignores receiveMessageWaitTime and always does long-polling:

https://stackoverflow.com/questions/53372107/aws-sqs-long-polling-doesnt-reduce-empty-receives#comment93651661_53379640

WDYT?

[pahud]

@sarisia

From what I see in the CFN doc

ReceiveMessageWaitTimeSeconds
Specifies the duration, in seconds, that the ReceiveMessage action call waits until a message is in the queue in order to include it in the response, rather than returning an empty response if a message isn't yet available. You can specify an integer from 1 to 20. Short polling is used as the default or when you specify 0 for this property. For more information, see Consuming messages using long polling in the Amazon SQS Developer Guide.

It is unclear to me if the default is 0 but short polling is the default behavior if undefined and the effect is just as setting this value to 0.

In terms of Lambda's internal SQS poller's behavior, we probably need to look up other document but I support to have a PR to update the default from 20 to 0.

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[sarisia]

I'll submit a PR later, thanks!

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